As long as the servo driving the elevator half has ample torque to drive the surface, and the control point is somewhere near the flight surface center, a single servo will work absolutely fine. People have no idea of how much extra torque we are using with servos on our planes that we will never have need for. I see mini servos used on the flight surfaces of 40 plus pound planes all the time, and as long as they are set up right they work fine.

I don't for a minute suggest that we use them on our 3D planes, but it was provided to illustrate a point. Metal gears, torque, excellent linkage and geometry, and a good power supply take precidence over servo quantity in most cases.

Pat